Spill port control for free-piston units



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INVIPINTOR May u, 1948. A. KALlTlNsKY f v 2,441,273

SPILL PORT CONTROL FOR FREE-PISTON UNITS Filed Aug. 23, 1944 4 Sheets-Sheet 3 ay M, 1948. A. KALITINSKY 2,44273 SPILL PORT CONTROL FOR FREE-PISTON UNITS Filed Aug. 23, 1944 4 Sheets-Sheet 4 FEG. 4,

HNVENTR atented May 11, 1948 SPILL PORT CONTRL FOR FREE-PISTON UNITS Andrew Kalitinsky, Eagleville, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application August 23, 1944, Serial No. 550,886

3 Claims. (Cl. 230-56) This invention relates to the control of spill ports in the compressor cylinders of a free-piston unit.

The copending application of Kalitinsky, Serial No. 550,884, led August 23, 1944, describes a freepiston unit, the compressor cylinders of which have a number of rows of spill ports, each row of which is individually controlled for maintaining th'e desired length of piston stroke. A feature of this invention is an arrangementfor automatically adjusting the rows of ports.

A. stroke indicator for indicating changes in the position of the end of the piston stroke is disclosed in the copending Kalitinsky application, Serial No. 550,883, led August 23, 1944, patented May 13, 1947, Pat. No. 2,420,483, in which a change in the position of the ends of successive strokes of the piston causes a change in pressure in a iluid. A feature of this invention is the automatic control of the spill ports from astroke indicator or master control of this type.

Another feature is the actuation of th'e structure by which the spill ports are opened and closed in response to changes in an operating characteristic of the unit such as a change in the length of the piston stroke.

Other objects and advantages will be apparent from the specication and claims, and from the accompanying drawings which illustrate an embodiment of th'e invention.

Fig. 1 is a sectional view through the freepiston unit.

Fig. 2 is a sectional view of the restraining linkage,

Fig. 3 is a. transverse section on line 3-3 of Fig. l, with a part of the band actuating mechanism shown diagrammatically.

Fig. 4 is a diagrammatic view of the master control and the actuating mechanism for the spill ports.

The unit shown includes an engine cylinder Ill having reciprocating pistons I2 and I4 to which compressor pistons I6 and I8 in cylinders'ZIl and 22 are integrally connected. Sleeves 24 and 26 attached to the compressor pistons complete the reciprocating piston assemblies. The sleeves in combination with stationary pistons 28 and 30 -form air spring cylinders.

The piston assemblies are moved apart by the burning of fuel injected into engine cylinder III through one or more nozzles 32. Air compressed the center of the engine cylinder by a linkage discharge from the cylinder without compres.

2 which may include racks 34 and 36, Fig. 2, ex-

tending from the piston assemblies and meshing with a pinion 38 on a shaft 40.

Intake manifold 42 which extends around the compressor and engine cylinders, conducts air to intake valves 44 in the heads'of the compressor f cylinders through which air alternately enters opposite ends of the cylinders. The compressed air -leaves the cylinders through discharge valves 46, also at opposite ends of the compressor cylinders and passes into a central scavenge chamber 48 and end chambers 50 and..52. These chambers may be interconnected by a scavenge manifold, not shown.

Compressed gas from the scavenge chambers enters engine ports 54 and 56 which are uncovered by pistons I2 and I4 at th'e end of the power stroke, thereby permitting air to be blown through the engine cylinder. Gas in the engine cylinder is discharged through exhaust ports 58 into exhaust manifold 60.

Each compressor cylinder hasa number of axially spaced vents 62, each in the form of a row of spill ports in the cylinders to permit air to sion. Each vent, or row of ports, may be individually controlled by a band 64, Fig. 3, extending around the cylinder between projecting ribs 66 extending from the cylinder, said band having spaced openings 66 for alignment with the spill ports. This band may be held against the cylinder by a spring 10 and may be moved angularly, to open and close the ports, by a, hydraulic motor 'I2 including a cylinder 'I4 and a piston 16 having its projecting rod I8 connected to a lug 80 on the band 'I'he particular port closure shown is claimed in the copending application of Kalitinsky, Serial No. 550,884, iiled August 23, 1944.

The intake manifold includes a housing 82 which may extend around the compressor cylinders, and end caps 82 and 84 on the housing formling passages to the intake valves at the outer ends of the compressors. The vents 62 openinto the intake manifold.

When the air being pumped by the compressor has a high density, as at sea level atmosphere, all the rows of ports are open and only a small quantity of air is compressed. As the density decreases, as when the compressor operates at altitude, one or more of the rows of ports may be closed, beginning with the end rows, thus increasing the effective volume of the compressor. The several rows of ports permit adaptation of the compressor to substantially any altitude or to any density of air being pumped.

The rows of ports may be automatically opened and closed from the master control which produces a pressure change in a control iluid in response to changes in an operating characteristic of the unit, suchasa change in the length of. piston stroke. Referring to Fig. -4 the master control is actuated by acam 88 turning with the pinion 88 as shown in Fig. 2, Since the pinion 38 is oscillated directly from the pistons the movement of cam 88 is proportional to the piston stroke.

Fluid under pressure from a constant pressure source enters a passage 88 in a casing 8u through a conduit 82. This passage intersects a bore 84 adjacent its outer end and a throttling screw 98 controls the rate of flow into bore 84. A branch passage 98 from passage 88 connects with a port in bore 94. A plunger |02 in bore 84 has a groove |04 which connects a port |06 alternately with port |00 or with a port |08. Port |08 is connected by a passage ||0 to the inner end of bore 84. Port |08 is connected by a channel H2 in casing 80 and in an adjoining casing-H4 to the inner (left-hand)` end of a bore I I6 in casing ||4. A piston ||8 in bore ||6 is moved to the right by a calibrated spring |20. A plunger |22 extends through the piston and carries onits projecting end a push rod |24. This rod carries a roller |28 held against cam 86 by a spring |28. Plunger |22 has a central passage |30 connecting with spaced grooves |32 and |34 in the plunger.` Groove |32 aligns with openings |38V in a sleeve |88 carried by piston ||8 and groove |34 is adapted to be uncovered by the end oi' sleeve |38 as the plunger is moved to the right by the cam as'the pistons approach the outer ends of their strokes.

Fluid under pressure from the right-hand end of bore 84 enters the right-hand end of bore ||8 through a connecting channel |40, moving piston ||8 to the left against the spring |20. As plunger |22 is moved to the right by cam 8G the groove |84 is uncovered by sleeve |88 to permit discharge oi?l uid from the right-hand end of bore H6. 'I'he pressure in the right-hand end of bore H8 varies in accordance with the compression of the spring and as the piston stroke becomes shorter the piston ||8 moves inward, increasing the spring tension and increasing the pressure at the end of bore 88.

Since the change in pressure on the right-hand end oi. plunger |02 is proportionalto the change in the location of the end position of the piston stroke,`the pressure on the inner (left-hand) end of plunger |02 which balances the pressure on the outer end must vary in the same manner. In this way the pressure in the discharge conduit |42 is proportional to the spacing of the actual end of the piston strc-ke from the extreme outer position of the piston, and changes in pressure ing piston rod |88 on the piston is connected toa valve plunger |82, Fig. 3, in a casing |84. This valve alternately directs fluid under pressure 30m an inlet port |88 to outlet ports |48 and |18 connected by ducts |12 and |14 to the opposite ends of the cylinder |14. When fluid is entering one one of cylinder 14 the other end ot the cylinder is vented by valve plunger |82 through one oi the vent ports |15 or. |14. The piston rod |82 may be connected to'a snap toggle including projecting arms |11 and |18 sliding in guides |84 and |82 with 4their outer ends connected by a spring |84. This arrangement assures movement of the valve to either ol.' its end positions to cause the control band 84 to be moved from the position in which the ports are fully closed to a position in which the parts are fully open.

If the piston stroke shortens, for example, ,the master pressure increases until it will overcome the iorce of spring |08 and the spring |84 and move valve plunger |82 to cause the row of ports to be open. With the ports open the stroke iengthens andthe master pressure-decreases. thus lowering the pressure on pistoni |88. Spring |84, however, acting on the snap toggle prevents spring |88 from moving piston |88 until the piston stroke has iensthened beyond' the increase `in length caused directly by the opening of the row of ports. Without this pressure diilerential, the reduction in master pressure resulting from opening the row of ports and thereby lengthening the stroke would immediately cause the ports to be automatically closed again.

Each row ol ports is controlled by a similar band and each baud is actuated by e. separate mechanism. As shown in Fig. 4 a second cylinder |88, similar to cylinder |84, has a piston |08 held in the position shown by a. spring |88, the strength of which is lower than the spring |48. This second device actuates an adjacent band and other devices may control the other-rows'. Since the outer master pressure varies in accordance with the changes in the piston stroke the rows ofports in this conduit will be proportional to changes.

in the outer end position of the piston stroke. This pressure and change in pressure are used to move the control bands for the rows of spill ports. The outer end of plunger |22 may reciprocate in a. chamber |44 having an outlet conduit |48 connected to a sump, not shown. The inner end of bore ||8 may be connected by a, conduit |48 to the conduit |48. A bellows |50 connected by a conduit |52 to passage |40 may be used for minimizing surges in the controls.

Discharge .conduit |42 may be connected to the end of a cylinder |54 in which is a piston |58. The piston is moved in one direction against may be successively closed by-Iadiusting the pressures of the springs |88 and |88 in the actuating devices for adjoining rows of ports so that the successive rows will be opened at diiIerent control pressures. As a result,- the rows orl ports may be closed successively in any predetermined order.

As the piston stroke shortens, the master control pressure increases to a pressure sumcient to shift the piston |88 which controls one ci the inner rows of ports and causes this row of ports to be opened, thereby reducing the eiective volume of the compressor. It the stroke continues to shorten. the control pressure increases enough to overcome the tension of the spring controlling the piston |58 for an adjacent row of ports, thereby causing a second row to be opened for further reducing the eiiective volume of the compressor and tending to increase the length of the piston stroke. v p

If the stroke lengthens. the reverse takes place and the rows of ports are successively closed. In the arrangement shown, the compressor being double-acting, the master control lshown may control the outer three rows of ports.l and a similaxmaster control. not shown. which is responsive to changes in the position of the .inner end oi' the iluid pressure by a spring |88. The project- 15 trated and described, but may be used in other 5 ways without departure from its spirit as defined by the following claims.

I claim:

1. In a free-piston unit, engine and compressor cylinders, a piston assembly moving in said cylinders, said compressor cylinder having a number of axially spaced circumferentially extending rows of spill ports, a band movable into a position for closing each row of ports and means for moving each band separately, in combination with means responsive to changes in the end position of the piston stroke for causing operation of each band moving means for closing the rows of ports individually.

2. In a free-piston unit, engine and compressor cylinders, a piston assembly reciprocating in said cylinders, said compres-sor cylinder having a plurality of circumferential rows of ports, and closure means for opening and closing the ports of each row separately, in combination with a master control adapted to vary the pressure of a fluid in response to changes in the piston stroke, and means responsive to the change in uid pressure for procuring operation of each of said port closure means separately, the master pressure for closing the ports being different from the master pressure at which the ports are opened.

3. In a freepiston unit, engine and compressor cylinders, a piston assembly reciprocating ln said cylinders, said compressor cylinder having at least one row of ports, and a band movable for closing or opening' said ports, in combination 6 with a master control for varying the pressure in a control fluid in response to changes in the length of the piston stroke, means actuated by said uid for causing the band to be moved to open or close the ports, and means maintaining a pressure differential between the port opening and port closing pressures of the fluid.

ANDREW KALITINSKY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 877,492 Doelling Jan. 28, 1908 1,254,781 Davol Jan. 29, 1918 1,481,358 Dwyer Jan. 22, 1924 1,579,782 Riesner Apr. 6, 1926 1,616,989 Redfield Feb. 8, 1927 2,016,613 Pescara Oct. 8, 1935 2,038,442 Pescara Apr. 21, 1936 2,064,976 Janicke Dec. 22, 1936 2,090,709 Steiner' Aug. 24, 1937 2,108,890 Jancke Feb. 22, 1938 2,139,425 Steiner Dec. 6, 1938 2,147,935 Steiner Feb. 21, 1939 2,414,744 Kalitinsky Jan. 21, 1947 FOREIGN PATENTS Number Country Date 237,170 Germany 1910 

